L u n a r E c l i p s e

Samuel Wat

Introduction:

We live in a world that seems so ordered; the Sun rises, goes across the sky and then sets. The Moon goes through its phases from new to full and back again. It all seems like clockwork, and then, something unusual happens that seems to throw the orderly timing of the cosmos into chaos. On a night when the moon rises full and beautiful, it starts to change, at first it is so subtle few notice it. But then,every so slowly, the moon begins to dim, and more alarming yet, it disappears...

Eclipses have even influenced history, and even today there are those who still attach ancient superstitions to an eclipse. But such are the few, today we know what causes lunar eclipses. And although it may seem a magic show of shadow and light and a disappearing act by the Moon, we know how the "magic" works, but we can still appreciate the beauty.

There are actually several type of lunar eclipses, total, partial and penumbral. The upcoming eclipse is the best kind, a total lunar eclipse. This kind can only take place when the Earth passes directly in front of a full Moon, thus casting its shadow on the Moon's surface.

There are two parts to the Earth's shadow, the penumbra, and the umbra. The penumbra is the outer part of the shadow where sunlight is not completely blocked. The penumbral shadow only dims the Moon every so slightly, in fact unless you are in very dark skies, you may not notice this part of the eclipse at all. The umbra is the actual shadow created by the Earth. You will notice the Moon getting darker from the leftside first. During the time when the entire Moon is in the umbra, it issaid to be in totality. Many people are surprised that the eclipsed moon is reddish but thereis a reason. Some of the sunlight passes through the Earth's atmosphere and is bent around behind the Earth and towards the moon. The shorter wavelengths of light is scattered and only the longer orange and red wavelengths reach the moon. It is usually just enough light to cast a coppery red hue on the Moon.

Now, we mentioned that there are other types of lunar eclipses. A partial lunar eclipse is when only part of the Moon travels through the umbral shadow of the Earth. Depending on how much of the Moon passes through, you may or may not notice this type of eclipse. A penumbral eclipse is when the Moon passes only through the penumbral shadow of the Earth.

Vocabulary:

Eclipse - The partial or complete obscuring, relative to a designated observer, of one celestial body by another.
Umbra - The completely dark portion of the shadow cast by the earth, moon, during an eclipse.
Penumbra - A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination.
Partial - When only part of the Moon travels through the umbral shadow of the Earth.

Credits to http://starryskies.com for lunar eclipse info.

Website made for Peabody school 8th grade science class of 08'

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